This invention relates generally to metal-cutting machines; more particularly it relates to milling machines of the type having a head which supports a spindle case that is movable in an axial direction with respect to the head. Specifically, it relates to an accessory for such milling machines which is designed to enhance the rigidity of the spindle and any tool mounted within the spindle for operations involving metal cutting, grinding, finishing, etc.
A major machine tool in most any machine shop is a milling machine of the type commonly referred to in the trade as Bridgeport-type mills. Such machines are characterized by having a rather heavy and therefore inherently stable frame which houses the basic drive mechanism for the machine. Attached to the front of such milling machines is a removable head, which is made removable so that it may be more readily taken off the frame for repairs, etc. Within the head is mounted a vertically movable spindle case or quill that supports a spindle in a rotatable fashion. The quill is adapted to move axially within the head for a distance of several inches--typically 5 inches--so that material may be cut through the action of longitudinal movement of the spindle as well as rotation of a tool mounted in the spindle. The head is typically mounted on a ram that can be made to translate with respect to the frame, and the head may also be rotated (or tilted) with respect to the forward end of the ram. Hence, a tool mounted on a Bridgeport-type mill can be selectively moved along any or all of three orthogonal axes.
Because of the axial (or longitudinal) movement of the quill (and its spindle) which is an inherent part of Bridgeport-type mills, the rigidity with which those mills may cut metal has always been less than might be obtainable--if movement of the spindle was not necessary or desirable. Nevertheless, the versatility of such milling machines has made them common "work horses" in nearly all machine shops that are adequately equipped, and there are now believed to be about 3,000,000 of such machines in the U.S. alone. While the basic Bridgeport design is definitely an accepted design, there has nevertheless remained a desire on the part of at least one person that the productivity of such machines be improved. It is an object of this invention to provide an increase in productivity by more firmly supporting the spindle case with respect to the machine head--such that tool chatter and the like can be reduced to the point of being essentially negligible.
Another object is to provide a modification for Bridgeport-type milling heads which will compensate for wear within O.E.M. bearings without requiring expensive re-building of those heads and replacement of the internal bearings, etc.
Another object is to improve tool life and increase the possible cutting speed of tools by minimizing tool vibration during traditional cutting processes.
These and other objects will be apparent from a reading of the specification and the claims appended thereto, as well as the figures provided herewith. In the specification, the following commonly understood abbreviations will sometimes be used as a short and convenient way of referring to certain words and phrases: ID for "inside diameter," OD for "outside diameter," and O.E.M. for "original equipment manufacturer.